In this thesis, barium ferrite nano particles were prepared by sol-gel method. Their structural and magnetic properties of samples have been investigated using thermogravimetric analysis (TG-DTA), X-ray powder diffractometer (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Field emission scanning electron microscopy (FESEM), ac susceptometer, Vibrating sample magnetometer (VSM) and vector network analyzer. At the first part, barium ferrite with PVA prepared. In order to prepare of this ferrite, the stoichiometric amount of iron nitrate (Fe(NO 3 ) 3 ), barium nitrate (Ba(NO 3 ) 2 ), polyvinyl alcohol (PVA) (C 2 H 4 O) n , citric acid (C 6 H 8 O 7 .H 2 O) and ethylenediaminetetraacetic acid (EDTA) (C 10 H 16 N 2 O 8 ) was used. TG-DTA curves indicated that the M-type hexagonal phase formation temperature decreases by the PVA addition. The XRD patterns showed that the pure hexagonal phase formed at 800 The XRD patterns with Rietveld analysis indicate the formation of single hexagonal phase and P6 3 /mmc space group. The crystallite size of samples was estimated to be about 40-70 nm by Williamson-Hall equation. These values are smaller than the crystallite size of the samples without PVA. Large particle agglomerations (with mean diameter of particles smaller than ) were observed in FESEM images. FTIR results confirmed the ferrite phase formation. In second part, the effect of Eu substitution on the structural and magnetic properties of Ba 1-x Eu x Fe 10.5 O 16.75 (x=0.0, 0.05, 0.1, 0.2, 0.25) samples was investigated. The XRD patterns with Rietveld analysis indicate the formation of single hexagonal phase and P6 3 /mmc space group at 1100 . Substituted samples have smaller crystallite size than pure one, which demonstrate the grain growth inhibitor role of Eu. SEM images indicated no differences among particle size of samples. It is found that there are large particle agglomerations, too. There are not any bound displacement and europium bound in FTIR spectra of substituted samples. It is observed that real part of magnetic susceptibility has no change with increasing ac field and frequency at room temperature. Susceptibility of samples with x doesn’t vary remarkably, too. The maximum enhancement in coercivity and minimum saturation magnetization was observed in the sample Ba 0.75 Eu 0.25 Fe 10.5 O 16.75 . The hysteresis loops indicate that doping enhances coercivity and decreases saturation magnetization. The measurements of reflection loss were done at X and Ku band frequency. We obtained higher reflection loss for x= 0.0 sample in the X-band and the ferrite with composition of x= 0.1 provides the best electromagnetic absorbing properties at Ku-band frequency. Thus substitution is useful to improve reflection loss at Ku-band frequency while substitution isn’t applicable to enhance the reflection loss at X-band frequency.
